{
  "affected": [
    {
      "package": {
        "ecosystem": "RubyGems",
        "name": "prosemirror_to_html"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.2.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2025-11-06T15:44:35Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Impact\n\nThe prosemirror_to_html gem is vulnerable to Cross-Site Scripting (XSS) attacks through malicious HTML attribute values. While tag content is properly escaped, attribute values are not, allowing attackers to inject arbitrary JavaScript code.\n\n**Who is impacted:**\n- Any application using prosemirror_to_html to convert ProseMirror documents to HTML\n- Applications that process user-generated ProseMirror content are at highest risk\n- End users viewing the rendered HTML output could have malicious JavaScript executed in their browsers\n\n**Attack vectors include:**\n- `href` attributes with `javascript:` protocol: `\u003ca href=\"javascript:alert(document.cookie)\"\u003e`\n- Event handlers: `\u003cdiv onclick=\"maliciousCode()\"\u003e`\n- `onerror` attributes on images: `\u003cimg src=x onerror=\"alert(\u0027XSS\u0027)\"\u003e`\n- Other HTML attributes that can execute JavaScript\n\n### Patches\n\nA fix is currently in development. Users should upgrade to version **0.2.1** or later once released.\n\nThe patch escapes all HTML attribute values using `CGI.escapeHTML` to prevent injection attacks.\n\n### Workarounds\n\nUntil a patched version is available, users can implement one or more of these mitigations:\n\n1. **Sanitize output**: Pass the HTML output through a sanitization library like [Sanitize](https://github.com/rgrove/sanitize) or [Loofah](https://github.com/flavorjones/loofah):\n```ruby\n   html = ProsemirrorToHtml.render(document)\n   safe_html = Sanitize.fragment(html, Sanitize::Config::RELAXED)\n```\n\n2. **Implement Content Security Policy (CSP)**: Add strict CSP headers to prevent inline JavaScript execution:\n```\n   Content-Security-Policy: default-src \u0027self\u0027; script-src \u0027self\u0027\n```\n\n3. **Input validation**: If possible, validate and sanitize ProseMirror documents before conversion to prevent malicious content from entering the system.\n\n### References\n\n- Vulnerable code: https://github.com/etaminstudio/prosemirror_to_html/blob/ea8beb32f6c37f29f042ba4155ccf18504da716e/lib/prosemirror_to_html.rb#L249\n- [OWASP XSS Prevention Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/Cross_Site_Scripting_Prevention_Cheat_Sheet.html)\n- [CWE-79: Improper Neutralization of Input During Web Page Generation](https://cwe.mitre.org/data/definitions/79.html)",
  "id": "GHSA-52c5-vh7f-26fx",
  "modified": "2025-11-06T15:44:36Z",
  "published": "2025-11-06T15:44:35Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/etaminstudio/prosemirror_to_html/security/advisories/GHSA-52c5-vh7f-26fx"
    },
    {
      "type": "WEB",
      "url": "https://github.com/etaminstudio/prosemirror_to_html/commit/4d59f94f550bcabeec30d298791bbdd883298ad8"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/etaminstudio/prosemirror_to_html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Cross-Site Scripting (XSS) vulnerability through unescaped HTML attribute values"
}